Method of repairing defective pump casings



June 9, 1964 c. F. FUNK ETAL 3,136,013

METHOD OF REPAIRING DEFECTIVE PUMP CASINGS Filed Feb. 8, 1961 TEMPERATURE IN Dlcfl 70 R INDUCTION /7 "E0 T1116 INVENTORS .I-QI. CHARLES F. FUNK euv L. FUNK JOHN E.FUNK

XMAQQATTORNEYIS United States Patent Ofitice Patenteddune 9, 1964 3,136,013 METHOD OF REPAIRING DEFECTIVE PUMP (IASINGS Charles Francis Funk, 11755 Sherbrook Drive; John Eugene Funk, 1506 Eugene St.; and Jack L. York, 4863 Elmwood Drive, all of Baton Rouge, La., and Eugene Funk, deceased, late of 1454 Arlington Ave., Baton Rouge, 1.21., by Marguerite Bourgeois Funk, Charles Francis Funk, John Eugene Funk, Guy L. Funk, and Margaret M. Funk, heirs Filed Feb. 8, 1961, Ser. No. 87,972 7 Claims. (Cl. 22203) This invention relates to a new and improved method of repairing defective surfaces, such as the worn interior shroud portions of centrifugal pumps, and the like.

Due to the adverse conditions imposed oncentrifugal pumps, such as by foreign matter in the fluid, and cavitation, the interior peripheral Walls in the area surrounding the impeller are subjected to continual abuse, and this shroud portion of a centrifugal pump casing accordingly is subjected to relatively rapid wear while the remainder of the pump casing remains in generally good condition. The life of a centrifugal pump casing is thereby determined, to a great extent, by the condition of the shroud portion of the casing adjacent the tips of the pump impeller blades.

In accordance with a feature of this invention, new and improved methods are provided for repairing worn or otherwise defective metal surfaces, such as the shroud portion of a centrifugal pump. The shroud portion of the pump casing is thereby strengthened and is' otherwise rendered useful for an extended period of time.

Another object of this invention is to provide a method for repairing the defective shroud portion of a pump casing by the fusion of thermit metal to this surface.

Still another object of this invention is to provide a method for repairing the defective shroud portion of a centrifugal pump wherein new and improved molding techniques are utilized.

Still further objects and advantages of this invention will become apparent in the specification, claims, and accompanying drawings wherein:

FIGURE 1 shows in partial perspective a defective pump casing which is partially prepared for repair;

FIGURE 2 is a perspective view similar to FIGURE 1 partially broken out, showing the pump casing partially prepared for molding; 1

FIGURE 3 is a view generally similar to FIGURES l and 2 showing the mold just prior to completion, wherein the molding sand is partially packed;

FIGURE 4 shows in perspective the pump casing and mold just prior to the introduction of thermit metal, or the like, into the area to be repaired; and,

FIGURE 5 is a partial perspective view of a portion of the repaired pump casing, showing the thermit metal fused to the defective shroud portion of the pump casing.

Reference is now made to the accompanying drawing wherein a pump casing having a worn or defective shroud portion 12 is cleaned to remove dirt, rust, grease, and other foreign matter. Carbon tetrachloride, air pressure, and other well-known expedients may be used to clean the pump casing and otherwise prepare it for repair.

Any holes in the pump casing are suitably closed, as by welding. The primer hole (not shown) which extends radially outward of the shroud portion of the pump casing 10, is closed off, as by tack-welding a suitable plug in place.

A metal consumable liner 14 is then placed in the shroud portion 12 of the pump casing 10, the liner 14 being located by a check templet, or the like. The liner 14 is then properly secured to the pump casing 10, for example, by a plurality of spaced-apart tack welds 16.

Various well-known metals are suitable for this purpose; and, such materials as Wax may alternatively be utilized, as is apparent.

After the consumable liner 14 has been properly positioned within the pump casing 10, wherein the inside diameter between opposite liner faces constitutes substantially the diameter of the finished shroud portion, the pump casing 10 is horizontally disposed on fire brick supports 17, as shown in FIGURE 1;

An annular, lower sand-retaining ring 18 is then placed generally concentrically about the outside of the pump casing 10, as shown in FIGURES 2 and 3. After the annular ring 18 has been so positioned, the interior and exterior of the pump casing 10 are packed with molding sand 20 for a portion of the height, preferably to a height slightly below the level of the consumable liner 14.

A plurality of holes 22 and 24 are burned through the liner 14, the holes 22 and 24preferably being spacedapproximately 45 apart. Additionally, the holes 22 and 24 are preferably of alternately varying size, as for example, one hole 22 will be 1'' in diameter, the next adjacnet hole 24 being 1 /2" in diameter, the third hole 22 being 1" in diameter, and so forth, as best shown in FIGURE 2.

An induction heating coil 26 is placed about the outside peripheral wall of the pump casing 10, and thermocouples 28 are attached to the outside of the pump casing 10 in spaced apart relationship therearound. Theinduction coil 26 is then connected to a suitable induction heating machine and the thermocouples are connected toa temperature indicator, as will be apparent.

A number of riser tubes 3% are then secured at their lower ends to the holes 22 in the liner 14. In a like manner, pouring tubes 32 are secured to alternate holes 24 within the consumable liner 14.

After the induction coil 26, thermocouples 28, riser tubes 30 and pouring tubes 32 have been positioned as previously described, the additional molding sand is tamped about the inside of the pump, with due caution being exercised to insure that the risers 30 and the pouring tubes 32 are kept in their proper positions.

An annular upper sand-retaining ring 34 is then placed on the upper side of the pump casing 10 and preferably resting thereon. After the molding sand has been tamped to a suflicient height, a slag-forming basin 36 is placed within the upper sand-retaining ring 34, the pouring tubes 32 being connected with apertures therein, as best shown in FIGURE 3. The tamping is then continued until such time as the level of the molding sand is substantially equal to the height of the upper surface of the upper sandretaining ring 34. In a like manner, the additional molding sand is added to the space between the lower sandretaining ring 18 and the exterior of the pump casing 10, whereby the induction coil 26 and thermocouples 28 are covered with molding sand. The discharge port of the pump casing 10 (not shown) is, of course, tamped with molding sand to prevent closing thereof during the actual welding process, as will be apparent. FIGURE 3 shows the mold in a partially completed condition.

After the mold has been completely formed, the riser tubes 30, the slag basin 36 and the pouring tubes 32 are removed from the completed mold, care being taken not to introduce sand into the shroud portion 12.

The upper area of the mold defined by the slag basin 36 and the exposed sand on the top of the mold are then heated with a gas torch until the surface is properly baked. The introduction coil 26 is then energized, the heating machine being set for a temperature of approximately 1000 F.

The temperature of the pump casing 10 is then preheated to approximately 1000 F. and held, for example, for approximately 45 minutes.

A crucible 38 (FIGURE 4) is then prepared for pouring, the crucible 38 being at minimum temperature of approximately 200 F. A crucible 38 is charged with a predetermined amount of thermit metal, and the crucible is moved over the area defined by the slag basin 36 by suitable means (not shown). A magnesium starter is then added to the thermit metal within the crucible to initiate the exothermic reaction of the metallic oxide and aluminum as will be understood.

After the temperature of the metal within the crucible 38 has been elevated by the chemical reaction therein, the crucible is tapped and the metal is passed into the recessed portion defined by the slag-forming basin 36 and through the passages defined by the pouring tubes 32 into holes 24 wherein the thermit metal is fused to the interior shroud portion 12 of the pump casing 10. In this regard, the consumable liner 14 is fused with the thermit metal whereby a smooth uninterrupted shroud 12' is obtained, the metal being fused to the defective shroud 12 as shown in FIGURE 5. After the slag has had time to solidify, which is about 30 minutes for each 500 lbs. of material, the upper and lower rings 34 and 18 respectively, are removed. In a like manner, the molding sand is removed from the exterior of the pump casing 10 and the thermocouples 28 and induction coil 26 are removed. The pump casing 10 may then be lifted with a chain fall or the like (not shown) and the sand is shaken out of the interior of the pump casing 10.

After the sand has been cleared from the inside of the pump casing 10, the risers and pouring hole rods may be cut from the pump. In a like manner, the primer hole plug is then removed, as well as the molding sand which has been placed in the discharge port of the pump casing.

It will, therefore, be seen that there has been provided by this invention a method of repairing defective pump casings in which the various objects hereinbefore set forth, together with many practical advantages, are successfully achieved.

As various possible embodiments may be made of the mechanical features of this invention, all without departing from the scope thereof, it is to be understood that all matters herein set forth or shown in the accompanying drawings is to be interpreted in an illustrative, and not in a limiting sense.

What is claimed is:

1. A method of repairing the defective interior surface of a worn pump casing and the like constructed of metal receptive to fusion with thermit metal, comprising the steps of providing a consumable liner having holes therein, placing said consumable liner in the shroud portion of the pump casing so as to define a space between the consumable liner and the interior shroud surface, placing pouring tubes and riser tubes in communication with the liner holes; packing the interior and exterior of the shell,

wherein the pouring tubes are connected to a slag basin and the riser tubes communicate withrthe atmosphere, removing the tubes, risers and slag basin after the mold is formed, preheating the pump casing, introducing reacted thermit into the slag basin, whereby the thermit metal 4. passes from the slag basin through the passages defined by the pouring tubes into the space between the consumable liner and the worn casing and fills the space and the shroud surface of the pump casing to provide a relined shroud portion of fused thermit metal.

2. Method defined in claim 1 including the step of heating the shell with induction coil.

3. Method defined in claim 1 including the step of attaching thermocouples to the exterior of the pump shell.

4. Method defined in claim 1 wherein the holes in the consumable liner are of different sizes.

5. Method defined in claim 1 wherein the consumable liner is metal and including the step of tack welding the liner to the shroud portion of the pump casing.

6. A method of repairing the defective interior surface of a worn pump casing and the like constructed of a metal receptive to fusion with thermit metal comprising the steps of providing an annular consumable liner having holes therein, placing said annular consumable liner in the interior shroud portion of the pump casing so as to define a space between the consumable liner and said interior shroud surface, mounting the pump casing in a generally horizontal plane, placing pouring tubes in communication with some of the liner holes and placing riser tubes in connection with other liner holes, mounting an induction coil adjacent the outside peripheral surface of the shell casing, placing a lower sand-retaining member about the outside periphery of the casing and packing molding sand thereabout, placing an upper sand-retaining member on the upper side of the casing and packing molding sand therein, and forming a slag basin at the upper end of the upper sand-retaining member in communication with the pouring tubes, removing the pouring tubes and riser tubes, preheating the casing by energizing the induction coil, introducing reacted thermit metal into the slag basin, whereby the thermit metal passes through the passages formed by the pouring tubes into the shroud space of the pump casing bounded by the interior surface of the pump casing and said liner, the metal fusing with the defective shroud portion thereof, and the liner being consumed by the thermit metal to provide a repaired shroud portion of fused metal.

7. Method defined in claim 5 wherein the consumable liner is metal and including the step of tack welding the liner to the shroud portion of the pump casing.

References Cited in the file of this patent UNITED STATES PATENTS 1,238,789 Kralund Sept. 4, 1917 1,934,901 Witting Nov. 14, 1933 2,358,090 Longoria Sept. 12, 1944 2,830,343 Shroyer Apr. 15, 1958 OTHER REFERENCES Thermit Welding for Fabrication and Repair, publ. by Metal & Thermit Corp., Broadway, NY. 5, N.Y., copy in Scientific Library received Mar. 31, 1947. Entire publication 32 pages, pp. 4, 7, and 9 pertinent. 

1. A METHOD OF REPAIRING THE DEFECTIVE INTERIOR SURFACE OF A WORN PUMP CASING AND THE LIKE CONSTRUCTED OF METAL RECEPTIVE TO FUSION AWITH THERMIT METAL, COMPRISING THE STEPS OF PROVIDING A CONSUMABLE LIENR HAVINGHOLES THEREIN, PLACING SAID CONSUMABLE LINER IN THE SHROUD PORTION OF THE PUMP CASING SO AS TO DEFINE A SPACE BETWEEN THE CONSUMABLE LINER AND THE INTERIOR SHROUD SURFACE, PLACING POURING TUBES AND RISER TUBES IN COMMUNICATION WITH THE LINER HOLES; PACKING THE INTERIOR AND EXTERIOR OF THE SHELL, WHEREIN THE POURING TUBES ARE CONNECTED TO A SLAG BASIN AND THE RISER TUBES COMMUNICATE WITH THE ATMOSPHERE, REMOVING THE TUBES, RISERS AND SLAG BASIN AFTER THE MOLD IS 